Electromagnetic sound translating device



1947- J. J. HYLAND ET AL 2,432,424

ELECTROMAGNETIC scum) TRANSLATING DEVICE Filed Aug 21, 1944 Fig 2INVENTORSV JOf/NJ HYl/JND WILL/AM a. MULDOON Patented Dec. 9, 1947UNITED STATES PATENT OFFlCE ELECTROMAGNETIC SOUND TRAN SLATING DEVICEApplication August 21, 1944, Serial No. 550,418

12 Claims. 1

This invention relates to improvements in sound translating equipmentand has particular reference to a telephone unit of the sound powered'type.

Known devices of this character usually comprise a field structureconsisting of one or more permanent magnets with which pole pieces areassociated and arranged so that their pole tips of opposite polarity areopposed to each other. Said opposed pole tips have their faces in spacedapart relation to receive therebetween opposite end portions of avibratory armature forming a part of' the motor assembly, and pivotallymounted intermediate its ends in a supporting struc ture about which thevoice coil of said assembly is wound in electromagnetic association withsaid aramature. One end of said armature is connected to a diaphragmresponsive to sound waves from an external source in the case of atransmitter, or responsive to mechanical impulses in the case of areceiver, said impulses being generated by the vibration of saidarmature. Heretofore, in the manufacture of such devices, difiicultieshave been encountered in making the same of sufiiciently ruggedconstruction to withstand shocks and yet have a sensitivity which willadequately transmit voice currents and be of a weight and size whichwill render the instrument practical for universal use in telephonework. Among these difiiculties are the structural formation andarrangement of the parts which increase the size and weight of theinstrument, the inability to secure rigid maintenance of the coilassembly, including the armature, in fixed relation to the pole pieces,and the inadequate protection of the armature against the effects of gunor other high pressure blast waves.

The present invention is designed to overcome the above mentioneddifiiculties by the production of an improved device of practical,rugged and efiicient construction which will hav the advantages ofsimplicity and ease of assembly, lightness of Weight, reduction of sizeparticularly with respect to its over-all height, and capable ofwithstanding extreme shocks without displacement of parts.

In carrying out the above objects, a structure is provided wherein thepole pieces are so constructed and arranged that the same will form thsole support for the elements constituting the motor assembly, andcombine to provide a recess for the reception of the voice coil and itsarmature so that the outer faces of the pole pieces will besubstantially in the same planes as the outer opposed surfaces of saidcoil, thereby materially reducing the over-all height of the unit. Inthe coil assembly, a simple and positive means is provided foraccurately locating 'the armature with respect to the pole tips and forlocking said elements together in such manner that lateral displacementof the armature relative to the pole pieces will be avoided, even underthe severest shock tests. Further, it is proposed to protect the armaturfrom the effects of positive blast waves by mounting a stop memher onthe upper pole piece in association with the adjacent end of thearmature shaft.

The inventive idea involved is capable of receiving a variety ofmechanical expressions, some of which are shown in the accompanyingdrawing; but it is to be expressly understood that said drawing isemployed merely to facilitate the description of the invention as awhole and not to define the limits thereof, reference being had to theappended claims for this purpose.

In the drawing;

Fig. 1 is a plan view of a telephone unit constructed in accordance withthe invention.

Fig. 2 is a transverse section on the line 2-2 of Fig. 1.

Fig. 3 is a similar section on the line 3-3 of Fig. 1.

Fig. 4 is a perspective View of the lower pole. piece forming a part ofthe motor assembly.

Fig. 5 is a similar View of the upper pole piece.

Fig. 6 is an exploded perspective of the armature and its support.

Fig. '7 is a perspective view of one of the permanent magnets.

Fig. 8 is an enlarged section of a detail taken through a portion of thearmature support, and

Fig. 9 is a transverse section through a modified form of diaphragmassembly.

In its preferred form, the motor assembly of the device comprises,generally, a magnet structure consisting of two permanent magnets Illarranged at opposite ends of a substantially rectangular voice coil Ii,it being apparent and within the scope of the invention that saidmagnets may be combined in a unitary structure, if desired. Extendingthrough said coil is the armature l2 supported for vibratory movementsby two elements in the form of parallel bars [3 of nonmagnetic material.Said bars are pro vided with recesses i l in the inner opposed facesthereof adapted to receive and have secured therein, by any suitablemeans such as solder introduced into openings i i in said bars, theextensions i5 projecting. from intermediate points of the side edges ofthe armature l2 and in a plane therewith, this manner of supporting thearmature being well known in the art. An ear I6 is formed at one end ofthe armature for connection to the shaft ll thereof. The armature andits supporting bars are insertable through and adapted to be secured inthe opening of the coil H, as will later appear. As customary, the endsof the armature project beyond adjacent ends of the coil so as to be inoperative association with lower and upper magnetic pole pieces 18 and[9 which, in the present instance, are of novel construction andarrangement, as will appear in the course of the description.

In order to overcome the possibility of a short circuit around each endof the armature l2 and through the bars i3 and pole pieces 18 and [9,said bars, which may be of brass, are chemically treated to provide themwith nonconducting surfaces. Such treatment may consist in theapplication of a coating of zinc carbonate or copper oxide to thesurfaces of said bars.

The motor assembly thus briefly described is mounted on the perforatedcover plate 20 and attached thereto by screws 2| which also secure theusual diaphragm 22 in position. At its center, said diaphragm issuitably connected to the lower end of the armature shaft l1 so that thediaphragm and armature will vibrate in unison. Provision for electricalconnections to the coil may be in the form of an insulated strip 23secured to the upper surface of the pole piece I8 and carrying terminals24 to which are attached the conductors 25 connected to said coil. Agasket 23 which may be of insulating material is secured to theperforated plate 20 and forms a seat for a cover (not shown) of theunit.

The lower pole piece 3 is in the form of a circular plate equal in sizeto the interior diameter of the cover plate 20 and, in accordance withone of the features of the present invention, said pole piece providesthe base for the entire motor assembly and combines directly with theupper pole piece [9 in rigidly and compactly securing together all partsof the motor assembly. Said pole piece [8 is provided therein with anopening 27 which forms an air space adjacent to diaphragm 22, thusproviding more suitable acoustic impedance by exposure of a portion ofsaid diaphragm. An extension 28 of said opening accommodates thearmature shaft H. is further provided with a second opening 29 fromopposed edges of which there extends laterally the two complementarypole tips 30 which are thus disposed within and spaced from the marginaledge of the plate, as distinguished from known constructions whereinsaid tips project from edges or ends of the pole piece. Each tip 30 isreduced along its face portion 3! to provide shoulders 32 at the endsthereof, and said shoulders of at least one of said tips are formed withrecesses 33 therein for a purpose which will presently appear.

The upper pole piece I9 is of substantially oval formation and hastherein an opening 34 similar to the opening 29 in the piece l8.Laterally projecting from opposed edges of said opening 34 are the poletips 35, the faces 36 of which are provided at their ends with shoulders31 similar to the shoulders 32 of the tips 39. Thus the tips are alsodisposed within the marginal edge of the pole piece i9.

When the pole pieces 18 and I9 are assembled, the pole tips thereof aredirected oward each other in opposed relation and constitute sets ofopposed polarity with their faces spaced apart Said pole piece all) toreceive therebetween the end portions of the armature I 2, Thusarranged, the shoulders 32, 3? of the two pole pieces are in suchaligned relation that they will receive and engage the ex tremities ofthe parallel armature-supporting bars 13 on opposite sides of the latterso as to aid in the maintenance of the armature and its support inproper position. It is highly important that, after assembly, the polepieces and the armature and its support be accurately located andrigidly held against relative lateral shifting such as might occur undersevere shocks and, to this end, the invention provides a simple andeffective means in the form of locking pins 38 projecting from the barsl3 adjacent the ends thereof and extending into the recesses 33 in theshoulders 32 of the pole faces 3|. Only two of said pins 38 and theircorresponding recesses are shown, but it will of course be understoodthat a pin and recess for each of the shoulders of both tips of the samepole piece may be provided, if desired or found necessary. When thesupporting bars [3 are thus interengaged with the pole piece l8, anyrelative lateral movements between the parts will be eliminated and thesame will be rigidly held together by the clamping action of theshoulders 32, 31, against the bars 13, said clamping action beingeffected in a manner to presently appear.

The openings 29, 34 in the pole pieces and the pole tips thereof,combine with the inner walls of the magnets in to form a recess for thereception of the coil H and, when in position therein, the inner andouter surfaces of said coil will lie substantially in the planes of theouter faces of the lower and upper pole pieces, respectively. Thisarrangement contributes materially to a reduction in the over-all heightof the unit and enhances the compactness of the structure withoutdetracting from its mechanical strength or acoustic eihciency. Further,the provision of the space formed by said recess permits of an increasein the height of the coil l l which may be at least equal to thecombined thickness of the plates from which the pole pieces I8 and I9are formed.

After the parts have been assembled as described, they are securedtogether by means of screws 39 which extend through the end portions ofthe upper pole piece I9 and into threaded engagement with the lower polepiece 18, the shanks of said screws projecting through slots 40 formedin the magnets l0. Tightening of said screws will draw the pole piecestogether into clamping engagement with the flux faces of the magnets it,and, at the same time securely clamp the shoulders 32, 31 of the poletips against the ends of the supporting bars l3.

Provision is also made for limiting movement of the shaft [1 under theinfluence of positive blast waves, this being accomplished by the simpleand effective expedient of mounting a stop member in the form of a setscrew 4| in the upper pole piece IS in direct alignment with and inspace relation to said shaft, where it is positioned for easy accesswhen it is desired to adjust the screw to vary the gap between it andthe adjacent end of said shaft.

In Fig. 9, a different form of diaphragm assembly is disclosed, whereinthe perforated cover plate 42 is centrally depressed to accommodate thediaphragm 22, and has its marginal edge 43 spun around the periphery ofthe lower pole piece I8.

What is claimed is:

l. A telephone unit comprising, in combination, a permanent magnetstructure, an assembly associated therewith and including a coil and anarmature, pole pieces each having tips extending laterally therefrom atpoints inwardly of the 7 margin thereof and in opposed relation to thetips of the other pole piece, said tips combining to form a recess forreceiving said coil with the outer faces of said pole pieces lyingsubstantially in the planes of outer opposed surfaces of said coil, andmeans fastening said pole pieces, coil and magnet structure in assembledrelation.

2. A telephone unit comprising, in combination, a permanent magnetstructure, an assembly associated therewith and including a coil, anarmature, supporting elements for the latter constituting the core forsaid coil, pole pieces having tips extending laterally therefrom andcombining to form a recess for receiving said coil, said tips havingportions of their faces engaging said supporting elements, meansconnecting said pole pieces for clamping said portions of said polefaces against said supporting elements, and means interengaging saidsupporting elements and pole tips for preventing relative lateralshifting between said parts both linearly and transversely of thearmature.

3. A telephone unit comprising, in combination, a permanent magnetstructure, an assembly associated therewith and including a coil, anarmature, supporting elements for the latter constituting the core forsaid coil, locking pins projecting from said supporting elements, polepieces having tips extending laterally therefrom and combining to form arecess for receiving said coil,

said tips having portions of their faces engaging said supportingelements and being provided in said portions with recesses for receivingsaid locking pins, and means connecting said pole pieces for clampingsaid portions of said pole faces against said supporting elements.

4. A telephone unit comprising, in combination, a permanent magnetstructure, an assembly associated therewith and including a coil, anarmature and two bars forming a support for said armature andconstituting the core for said coil, locking pins projecting from saidbars, pole pieces having tips extending laterally therefrom andcombining to form a recess for receiving said coil, said tips beingformed in their faces with shoulders for receiving said bars and havingrecesses in said shoulders into which said locking pins project, andmeans connecting said pole pieces for clamping said shoulders againstsaid bars.

5. A telephone unit comprising, in combination, a motor assemblyincluding a permanent magnet, a coil and its armature, a support forsaid armature, pole pieces associated with said elements, and lockingmeans between said support and one of said pole pieces for preventingrelative lateral displacement of said parts in different angulardirections.

6. A telephone unit comprising, in combination, a motor assemblyincluding a permanent magnet, a coil and its armature, a support forsaid armature, and pole pieces associated with said elements, one ofsaid pole pieces constituting the supporting base for said assembly andhaving tips extending laterally therefrom inwardly of the marginal edgethereof, securing elements clamping said pole pieces against said magnetand said armature support, and locking pins on said support extendinginto one of said pole pieces for preventing relative lateraldisplacement of said parts.

7. A telephone unit comprising, in combination, a motor assemblyincluding a permanent magnet, a coil and an armature associated withsaid magnet, a support for said armature, a pole piece associated withsaid support, and means to prevent lateral displacement between saidsupport and pole piece, said means including pins projecting from oneinto the other of the latter two elements.

8. A telephone unit comprising, in combination, a motor assemblyincluding a permanent magnet, a coil and an armature associated withsaid magnet, a support for said armature, a pole piece associated withsaid support, one of the last two named elements having recesses thereinfor receiving portions of the other element, and means to lock saidsupport and pole piece against relative lateral displacement, said meansincluding pins projecting from one of the last named elements into theother.

9. A telephone unit comprising, in combination, a motor assemblyincluding a permanent magnet, a coil and an armature, and pole piecesassociated with said armature, both said pieces comprising platesprovided with openings opposed edges of which are bent laterally to formpole tips between which said armature extends, and the plate of one ofsaid pole pieces constituting the supporting base for said motorassembly,

10. A telephone unit comprising, in combination, two pole pieces eachhaving tips projecting laterally therefrom and toward the tips of theother pole pieces and combining to form a space therebetween whichextends through said pole pieces, a coil mounted in said space, and anarmature mounted between the tips of said pole pieces and extendingthrough said coil.

11.A telephone unit comprising, in combination, two opposed pole pieceseach having tips projecting laterally therefrom and combining to form aspace therebetween which extends through said pole pieces, a coilmounted in said space and being of a height greater than the distancebetween the inner opposed surfaces of said pole pieces, and an armaturemounted between the tips of said pole pieces.

12. A telephone unit comprising, in combina tion, an armature support,pole pieces arranged on opposite sides of said support and each havingtips projecting laterally therefrom and combining to form a spacetherebetween which extends through said pole pieces, a coil mounted insaid space, and a balanced armature carried by said support and arrangedbetween the tips of said pole pieces.

JOHN J. HYLAND. WILLIAM J. MULDOON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,562,252 Pihl Nov. 17, 19251,671,105 Farrand et a1 May 29, 1928 1,830,160 French et al Nov. 3, 19311,870,446 Foley Aug. 9, 1932 1,871,739 Ringel Aug. 16, 1932 2,245,039Lilja June 15, 1941 2,343,859 Baldwin Mar. 14, 1944 2,391,627 HowellDec. 25, 1945

